Electric protective system



Jan.8,1929." 1,698,337

I B. H. LEESON AL ELECTRIC PROTECTIVE SYSTEM Filed June 23, 1926 n 1!: rats I Paiemteei" BRUCE HAMEE meson, a? TYNE wumm ere Ben- CGMBE, mm. mm, esszenees TO A. zelsyeordm CQIE-ZPAHY mmmzz, exs BUmI-em-mmm, ENGLAEZD, eewzmuw BY-"$523K.

Aeplicatiee filezi F1116: 1925, Serial Kc 213,0?7, and Great 3511mm 311119 '3,

This invention re ates J! an electric pruease a duplicate ceii relay is empioved at each iective pysiezg fer a 1 eder 01OtheliCOIldllCtOl end, Lhe izwo coilsbeing garevide fespeetive- UZ of condmtters(hereinafter referred to fiy in the cempaz 011 core ail-i in .the pilot 55 for cenvenience a feeds-1") 3115.113 10256 core. The eompenset' eenductgr shguld pm-tii'uizu' re rence is a balanced pmiwective in ibis arrangement 'ep i it d at or gvgtgjn j F M 1 th ndavy windings (2f ear the geint givulg equefiw capacity curcurreni u'ansfern'lers the rent ea 'ieci by $1 5 int care ead its comare so connecined into a, o-coz'e pi ie, eireui'ij penioil gore. 59 that there is normally a bwnmce of U. Q 1 10 in. that circuit Such system is die in the U. S. patent is Hunter and 631" it is Wei known that dii iiculties have arisen 3 in various. types sf 2. eased protective sys- 1e invention is eepeeieuy apgiicfiie to a 1-5 tems (espeeieily when me ilaf, wires are of two-core pilou prateetive s M great length} swing to the capacity currents a 'fiowil in $119 piioah eircuit 2116 one known e n, 1 methoc of dealing Wiih these liicuities is faults by providing 1;

to provxde each p lot core with e severed or a prmee'ive open-eir aim-: cempensating cenducioi'.

The present in ention has far its object to Jide simpie Rent eumpens v ing i501 fine Lc i'zy e ants in e The inventic may be carried inte practice baiance l' praise e systemempieying twe in varieus ways, but z'zwo alternative core pile-t six-e1 meets easel-ding theret-e a1 dieg 'emm In the eroiec'iwe (A by way 035 exem oie respectively lnve'n 011 :0

filing device so s of the feeder on the second end 2 0f the accompa y ng draw" p lot ircuit and the actual ar- -ee trensfez feeder A conneetdjo 4S and the eyei'a 'ing coil 4 hero-core pilet circuit C8115] trippingrelay Theoretiee C in sud at there ienormally sensitive anew "19m 1, for the 1 balance 0 he pi'iet circuit. epen-circuitcd 1 its 11 Y .f in the a Fights: i one oi the 95 pmci'ce the spemeinuiting point y b nit contains each L near one end of the pilet care witheut a,

i-1 N Y W j I, I I y a h. .uppmg lelay preemely illui-ictlng me sens etn 'eness 01 3 e 7 e111 x for a airrapgemeni, eder 1 Suz'i'eundin n s: confine 4 f sheeih E 109 "ereri at M, nliermeiiiate peint :8 which be new we This sheath E is com nested :2: ea be operating sail ef the as. ..l.-=-; e11; firamiermer 'secondarywin' A A A A diverter relay F of the brea contact type is connected across the secondary windings ateach end,

this relay acting in the known manner to control the scnsitiveness of the adjacent tripping relay D.

in this arrangement the capacity currents are free to flow in the unslieathed pilot core C which does notcontain the tripping relays I) and also in the compensating sheath E, but no capacity current flows through the relay coils D. D

In the arrangement of Figure 2 the compensating sheath of Figure 1 is replaced by a into the companion core G. In other respects the arrangement is identical with that of Figure l,

In this arrangement the capacity currents flow freely in the second pilot core C and also How in equal amount through the first pilot core B and its companion core (i. Owing to the equality of capacity current flowing through the cores B and G, the two coils H H of the tripping relay also carry equal currents and the relay therefore remains unaffected by the capacity currents.

It will be understood that modifications may be made in these arrangements Without departing from the scope of the invention.

What we claim as our invention and desire tosccurc by Letters Patent is 1. A balanced electric protective system, including in combination a two-core pilot circuit, protective current transformers disosed at the ends of the protected circuit and aving their secondaries so connected in the pilot circuit that there is normally a balance.

- of E. M. F.s therein, tripping devices associated with the pilot circuit and acting when operated to cut out the protected circuit at both ends, and means associated with'pne only of the two pilot cores whereby the tripping devices remain unaffected by capacity currents flowing in the pilot circuit.

2. A balanced electric )rotective system, including in combination a two-core pilot circuit, protective current transformers disposed at the ends of the protected circuit and having their secondaries so connected in the pilot circuit that there is normally a balance of E. M. F.s therein, relays connected in the pilot circuit and acting when operated to cut out the protected circuit at both ends, and a compensating conductor which is associated with one only of the two pilot cores and is severed or opcn-circuited so that no current means? can flow through it from end to end, the arrangement being such that the relaysremain unaffected by capacity currents flowing 1n the pilot circuit.

3. A balanced electric protective system,

including in combination a two-core pilot circuit, protective current. transformers disposed at the ends of the protected circu t and having their secondaries so connected 1n the ilot circuit that there is normally a balance of E. M. Ffs therein,'tripping devices asso ciated with thepilot circuit and acting when operated to cut out the protected circuit at both ends, and a compensating conductor which is associated with one only of the two pilot cores and is in the form of a severed or open-circuited companion core disposed adjacent to such pilot core, the arrangement bei'ng such that the tripping devices remain unaffected by capacity currents flowing in the pilot circuit.

i. A balanced electric protective system, including. in combination a two-core pilot circuit, protective current transformers disposed at the ends of the protected circuit and having their secondaries so connected in the pilot circuit that there is normally a balance of E. M. F.s therein, a compensating conductor which is associated with one only of the two pilot cores and is in the form of a se vcrcd or open-circuited companion core disposed adjacent to such pilot core, and a relay at each end of the pilot circuit acting when operated to cut out the protected circuit at both ends, each relay having two operating coils one of which is connected in the pilot core whilst the other is connected in the companion core.

5. A balanced electric protective system for a three-phase feeder, including in combination a group of protective current transformers at each end of the protected circuit having their secondaries so connected in series with one another that the three phases of the feeder have different inductive effects on the secondary circuit, a two-core pilot circuit into which the transformer secondaries are so connected that there is normally a balance of E. M. FrS in that circuit, tripping devices associated with the pilot circuit and acting when operated to cut out the protected circuit at both ends, and means associated with one onlyv of the two pilot cores whereby the tripping devices remain unaffected by capacity currents flowing in the pilot circuit.

6. A balanced electric protective system for a three-phase feeder, including in combination a group of protective current transformers at each. end of the protected circuit havlng their secondaries so connected in series with one another that the three phases of the feeder have dilleren't inductive effects on the secomlary cir uit, a t\ .'ocore pilot circuit into which the lran fornu'r secondaries are so connected that there is normttlly a balance of E. M. F.s in that circuit, relays connected in the pilot circuit and acting whenoperated to cut out the protected circuit at both ends, and a-compensating conductor which is associated Withone only of the pilot cores-and is'severed or open-circuited so that no current can flowthrough it from end to end, thearrangement being such that the relays remain unaffected by capacity currents flowing in the pilot circuit. 1

7. A balanced electric protective system for a three-phase feeder, including in combination a group of protective current transformers at each end ofthe protected circuit having their secondaries so connected in series with one another that the three phases of the feeder have different inductive effects on the secondary circuit, a two-core pilot circuit into which the transformer secondaries are so connected that there is normally a balance of E. M. F.s in that circuit, a compensating conductor which is associated with one only of the two pilot cores and is in. the form of a severed or open-circuited companion core disposed adjacent to such pilot core, and a relay at each end of the pilot circuit acting when operated to cut out the protected circuit at both ends, each relay having two operating coils one of which is connected in the pilot corewhilst the other is connected in the companion core.

In testimony whereof we have signed our names to this specification.

BRUCE HAMER Lnnson.

REGINALD WILLIAM Ruins. 

